3.1. Paleomagnetic Results
The samples were demagnetized generally up to 20 mT (for details see
Supporting Information Figs S2) which removed the viscous remanent
magnetization (VRM) component causing a change in the direction of
remanent magnetization during such demagnetization for most of the
samples. This soft VRM component in the samples has a mean D: 13.8° and
I: 56.8° values which is close to the present day’s Earth’s magnetic
field direction values for the Czech Republic (D: 4.4° and I: 66.8°)
(see Supporting Information Figs S3).
The intensity of the natural remanent magnetization (NRM) of the samples
varies between 8.5-34.1e-3 A/m. Median destructive field (MDF) values
where samples lost half of its magnetization range between 5-8 mT for
the samples. NRM intensity and MDF values of the samples are shown in
Supporting Information Figs S3. The maximum angular deviation (MAD)
values for Matuyama and Brunhes sections are between
0.3o-5.4o (Fig. 5a). These values
for the transition section are between
0.7o-5.3o which is relatively
reliable for the detection of the migration of the paleomagnetic vector
from reversed to normal polarity (Fig. 5a). The trend of the MAD values
increases across the transition which can also be seen in the other
studies (Sagnotti et al., 2014; Okada et al., 2017) (Fig. 5b).
In this study, paleomagnetic data showed inclination values changing by
approximately 90o when measuring the sediment from
12.8 to 7.1 cm depth (Fig. 6). This revealed the transition nature of
the Matuyama-Brunhes magnetic reversal in Za Hajovnou cave. Below this
depth, there is a Matuyama section which has inclination fluctuations
between -6.3o-88.7o (Fig. 6).
Inclination angle changes between
33o-65.9o for Brunhes section above
transition (Fig. 6). Also, the transition from reversed to normal
polarity can be seen in declination data with similar depth. It has more
frequent oscillations which show ~180° change from
reversed to normal polarity between 2.5-9.2 cm depth (Fig. 6b). Despite
the fluctuations, the intensity values of ChRM which can depend on the
concentration variation of magnetic carriers of every individual sample
were decreasing for the Matuyama section from the bottom to the
transition between 35.1-15 cm depth (Fig. 6). After the transition from
reversed to normal polarity, these values kept increasing which can be
seen in the Brunhes section between 7.1-0 cm depth (Fig. 6). Fig. 6
shows the data in comparison with other studies that consisted of
various sediment types and locations around the world. The depth of the
data sets was normalized considering the transition zone and differences
of sedimentation rate for each study and is not given in Fig. 5, 6. Even
though there are some differences in absolute values, comparisons of
this data set with other studies showed that fluctuations and frequency
of fluctuations in our data are consistent with other data sets and
serves as a supporting argument for Matuyama-Brunhes magnetic reversal
in Za Hajovnou cave (Fig. 6).